"Kent, Russell" wrote:

John Slade wrote:

[snip]

As I passed through 5800 with 36 MAP I noticed something

interesting.

[snip]

At 5900 rpm and 38 MAP it was even smoother.

[snip]

I backed off - ok chickened out - at 6100 rpm and 185 kts indicated
with a 44 MAP.

[snip]

By the way, perhaps I should mention that the manual wastegate
was wide open for the entire flight."

Russell Kent commented:

????
How can he get such MAPs with the waste gate wide open?  I would

expect

that a *properly working* waste gate should yield MAPs close to
atmospheric when fully open.

Paul Lamar replied:

The waste gate on the stock turbo is too small. The stock turbo
relies somewhat on turbine inertia and the back pressure of the
muffler to limit boost.

So what you're saying is the stock waste gate is not working properly,
in that it is undersized for continuous high power operation.

Russell Kent

I think so Russell. The flapper is limited to about 15 degrees open
as it hits the turbo charger back panel.

Here are my suggestions for improving it.

Paul Lamar

Paul, John Slade had his turbo done by Turbonetics in Australia, and with
the waste gate open all the time, he is getting boost in the 40's. I'm
thinking of removing the waste gate all together, or cutting half of the
flapper and leaving one of the ports open all the time?
Bulent

yes I know.
See my previous message. I would not permanently open it all the way.
Add another 3 inch exhaust pipe directly behind the waste gate to allow it
to open to a full 90 degrees. I'll do a 3D tonight as I need to go to
the machine shop.

Paul Lamar

Another reason the waste gate is not working well is the Aussies improved the 
compressor flow rate at a given turbine RPM so boost is higher at a given 
exhaust gas flow rate. That was a positive thing to do as it lowered
turbine RPM for a given boost level. That in turn should reduce the 
centrifugal force and the stress on the turbine blades.

Two 3 inch tubes won't fit. Here is a 3D with one 2.75 inch tube and one two inch
tube. Also a one inch thick spacer that allows the waste gate to open to about
45 degrees. The spacer can be flame cut from one inch thick steel plate or 
possibly plasma cut. Laser cutting does the best job but I don't expect it
can do one inch plate. Also it could be pieced together with spools and short
pieces of 1/4 inch thick, ones inch wide plate.

The easiest thing to do is just control the boost with the throttle like John 
and Dave Leonard are doing now. 

Paul Lamar
 
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